Reactions of triene-conjugated diazo-compounds: reaction paths from o-(1,3-dienyl)aryldiazomethanes to 3,8-methano-1,2-diazocines and to pyrrolo[2,1-a]phthalazines via intramolecular (3 + 2) and 1,1-cycloaddition reactions

Abstract

The reaction paths followed by the triene-conjugated diazo-compounds 7, which have α,β aromatic and γ,δ; ε,ζ olefinic unsaturation, depend strongly on the nature of the substituents R¹ and R². Those with R¹,R² = (CH₂)₃, 7a–e, react at room temperature via an intramolecular (3 + 2) cycloaddition reaction of unprecedented regioselectivity to give the bridged benzodiazocines 18a–e in high yield. Those with R¹ = Me and R² = Ph, 7f and 7g, react at 80 °C to give the hydrocarbons 19f,g and, via new chemistry, the pyrrolo[2,1-a]phthalazines 24f,g. The structures of compounds 18a, 19a and 24f have been determined by X-ray crystallography.